1. Field of the Invention
The present invention relates to a surface modification method using a plasma source ion implantation technique to improve surface properties and surface conductivity of 3-dimensional bulk polymers.
2. Description of the Related Art
Conventionally, to improve surface electrical conductivity of 3-dimensional bulk polymers, a method for evaporating a metallic conductive layer on the surface of bulk polymers, a method using conductive bulk polymers (Korean Patent No. 190,269) and a method of adding conductive filler such as carbon black when manufacturing bulk polymers (H. Tang, Z. Y. Liu, J. H. Piao, X. F. Chen, Y. X. Lou and S. H. Li, Journal of Applied Polymer Science, the 51st volume, 1,159 pages, issued on 1994) have been widely used. However, the conventional methods have various problems, especially, weak adhesive strength between bulk polymers and metallic sheet, and restricted conductive bulk polymers and complexity of process. Meanwhile, recently, a method of using high energy particle beam such as electron beam, ion beam or others (G. Marletta, C. Oliveri, G. Ferla and S. Pignataro, Surface Interface Analysis, the 12th volume, 447 pages, issued on 1988) is disclosed and used. Such particle beam can increase electrical conductivity of polymer surface, but must use an accelerator of a high price and the surface of three-dimensional sample is difficult to be treated uniformly.
A plasma source ion implantation technique using plasma and high voltage pulse (U.S. Pat. No. 4,764,394 and Korean Patent Nos. 137,704 and 217,538) is to modify the surface by implanting ions into the surface of 3 dimensional samples uniformly. The technique is very effective on the surface modification of metallic samples and on the impurity doping of semiconductors and very suitable for improving hydrophilicity or hydrophobicity of polymer surfaces.
In general, if high voltage pulse is applied to a sample stage, on which samples are put, ions are accelerated from the plasma by the electric field due to high voltage, so that the ions are implanted into the surface of the samples uniformly. However, as the 3-dimensional bulk polymers are nonconductors in which an electric current does not pass, the method of simply applying high voltage to the sample stage does not provide an effective ion implantation.
It is, therefore, an object of the present invention to provide a method for surface modification of 3-dimensional bulk polymers, which is capable of implanting plasma ions into surface of 3-dimensional bulk polymer sample by mounting a metallic grid having the electrical conductivity over a sample stage to modify the polymer surface and to improve the electrical conductivity of the polymer surface.
The principle for ion implantation into the surface of the 3-dimensional bulk polymers is as follows. That is, if negative high voltage pulse is applied to the metallic grid around the polymer samples, ions are extracted from the plasma and accelerated toward the grid. However, most of the ions pass the grid and collide with the surface of the polymer sample of high energy without colliding with the grid. Therefore, the method applying the high voltage pulse to the grid around samples allows ions to be implanted into the surface of 3-dimensional bulk polymers uniformly, so that the ions implanted in high energy modify the surface of the bulk polymers to improve the electrical conductivity effectively.